DEVICE FOR ADMIXING A PROCESSING AGENT TO A PULP SUSPENSION

Abstract: A device for admixing a processing agent to a pulp suspension. The device comprises a cylindric lower portion (10) of a vessel with an agitator (11) fitted into the wall of said vessel portion, which agitator is intended to bring about a pulp flow across the vessel portion (10). Means are provided (13) for the supply of the processing agent to the pulp flow. A flow divider (15) is located in the vessel portion (10) diametrically opposite the agitator (11). Said flow divider (15) comprises a substantially vertical front distribution edge (16) and arc-shaped surfaces (17) extending from the distribution edge (16) one in each direction, which surfaces are substantially vertical and join the wall of the vessel portion (10).

Description: Device for admixing a processing agent to a pulp suspension This invention relates to a device for admixing a processing agent to a pulp suspension in a vessel. The processing agent can consist of liquids and chemicals, substantially in fluid state, for dilution or other types of processing. A persistently uniform and proportional admixture of the processing agent to the pulp is of decisive importance for achieving an accept¬ able result at all types of pulp processing. In known arrangements the processing agent is admixed in the lower portion of a pulp vessel. The pulp concentration in the pulp vessel normally is 10-20%, which must be lowered to about 2,5-8% for mak¬ ing it possible to pump the pulp suspension out from the vessel. When the pulp vessel is used as bleaching tower, it is necessary to supply dilution through a number of nozzles in a restricted lower portion of the tower. The bottom zone of the tower there is restricted by a cylindric cone for guiding the processing agent in a circular way. A high pulp concentration, for example 12%, in the vessel renders it problematic to achieve a uniform admixture. In order to reduce the problem, the size of the vessel has been reduced. Such ar arr¬ angement even requires much energy, due to an incomplete admixture technique and to an unsuitable configuration of the bottom. According to the present invention, the aforesaid problems are eliminated, in that the processing agent is supplied and distributed centrally and the flow is improved. An improved mixing result is achieved, and at the same time the energy consumption is lowered to a minimum. The characterizing features of the invention are apparent from the attached claims The invention is described in greater detail in the following, with reference to the accompanying Figures illustrating an embod¬ iment of the invention. Fig. 1 shows the lower portion of the processing vessel, Fig. 2 is a section according to II-II in Fig. 1, Figs. 3 and 4 show in a schematic manner different alternatives of the embodiment according to Figs. 1 and 2. The mixing vessel according to Fig. 1 comprises a cylindric lower portion 10. An agitator 11 is fitted into the wall of the lower portion of the vessel. The agitator 11 comprises a propeller 12, which is intended to bring about a pulp flow across the vessel portion 10 simultaneously as a processing agent is supplied to the pulp flow. According to the embodiment shown, the processing agent is supplied through a pipe 13 located above the suction side of the agitator 11, and an inclined screen 14 is located in the vessel above the pipe 13. Said screen 14 is intended to distribute the in¬ going processing agent on the suction side of the agitator 11 and at the same time to prevent air to be sucked in from the surface of the pulp suspension in the vessel. There is risk of air being sucked in when the level in the vessel approaches the level of the agitator. As an alternative, the propeller agitator can be designed in a different way, for example as shown in patent application SE No 9202011-4. Diametrically opposite the agitator 11, the lower portion 10 of the vessel is formed with a flow divider 15. A substantially vertic¬ al distribution edge 16 on the front of this flow divider 15 is located on the central line of the agitator 11 at a distance from the wall of the vessel portion 10. Two arc-shaped substant¬ ially vertical surfaces 17 extend, one in each direction, from the distribution edge 16 outward to the vessel wall which these surfaces 17 join substantially tangentially . The surfaces 17 are symmetrical as regards the distribution edge 16 and are defined upwardly by an inclined plane 18 forming an angle v with the vessel wall. The arc-shaped surfaces 17 preferably are cylindric with a radius r which is 20-25% of the diameter D Df the vessel portion 10. The center axis of each of the arc-shaped surfaces 17 and the distrib¬ ution edge 16 should be located in the opposed half of the vessel portion 10 in relation to the agitator 11, but the distance between said center axis and, respectively, distribution edge and the imaginary plane dividing the vessel portion 10 into two halves should be smaller than 20% of the diameter D. The height ji of the distribution edge 16 should be 10-20% of the diameter D, counted from the vessel bottom. The highest point where the inclined plane 18 joins the wall of the vessel portion 10 should be located at a height H above the vessel bottom, where H lies in the interval 40-60% of the diameter D. The angle v_ determined by the difference between the heights Jh and H should be about 45 . Due to the design of the lower portion 10 of the vessel provided with a flow divider 15, the throw length of the agitator 11 is shortened and at the same time the pulp flow is divided into two partial flows of equal size. These partial flows flow back along the vessel wall and further to the suction side of the agitator 11 where simultaneously the inclined plane 18 produces a certain upward deflection. The pulp flow guided in this manner yields a very effective mixing and requires less energy supply than mixing arrangements heretofore used. The invention, of course, is not restricted to the embodiments shown, but can be varied within the scope of the invention idea.

Claims: Claims 1. A device for admixing a processing agent to a pulp suspension, comprising a cylindric lower portion (10) of a vessel with an agit¬ ator (11) fitted into the wall of said vessel portion (10) , which agitator is intended to bring about a pulp flow across the vessel portion (10) , and a means (13) for supplying the processing agent to the pulp flow, c h a r a c t e r i z e d i n that a flow divider (15) is located in the vessel portion (10) diametrically opposite the agitator (11) , which flow divider comprises a subst¬ antially vertical front distribution edge (16) and arc-shaped surfaces (17) extending from the distribution edge one in each direction, which surfaces are substantially vertical and join the wall of the vessel portion (10) . 2. A device as defined in claim 1, c h a r a c t e r i z e d i n that the arc-shaped surfaces (17) join the wall of the vessel portion (10) substantially tangeπtially. 3. A device as defined in claim 1 or 2, c h a r a c t e r ¬ i z e d i n that the distribution edge (16) is located in the opposed half of the vessel in relation to the agitator (11) . 4. A device as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that the distribution edge (16) is located on the central line of the agitator (11) , and the arc-shaped surfaces (17) are symmetrical in relation to the distribution edge (16) . 5. A device as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that the arc-shaped surfaces (17) are cylindric with a radius r_ which is 20-25% of the diameter (D) of the vessel portion (10) . 6. A device as defined in any one of the preceding claims, c h a r a c t e r i z e d i n that the arc-shaped surfaces (17) are defined upwardly by an inclined plane (18) forming an angle (v) with the wall of the vessel portion (10) , that the height (h) of the distribution edge (16) is 10-20% of the diameter (D) of the vessel portion (10) , and the highest connection height (H) of the inclined plane (18) to the vessel wall is 40-60% of said diameter (D) .

Inventors: FORSLUND KJELL, FORSLUND, KJELL
Applicants: FORSLUND KJELL, SUNDS DEFIBRATOR IND AB, FORSLUND, KJELL, SUNDS DEFIBRATOR INDUSTRIES AB
Application year: 1994
Main classification: B01F3
IPC codes: B01F3, B01F5, B01F7, B01F15, D21B1, D21D5